<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var x;
        console.log(x)
        var str1 = "hello word";
        var str2 = 'hello word';
        console.log(str1);
        console.log(str2);
        var str3="小明说：'小红真漂亮'";
        console.log(str3);
        // 字符串替换
        var str="java"
        // 1.下面代码执行顺序  先执行等候右侧代码 然后赋值给左边变量
        // 2.js字符串的加法是拼接字符串
        str =str+"script";
        console.log(str);
    </script>
</body>
</html>